Understanding Mendel's Theory of Heredity

1. Chapter 12; Section 2Mendel’s Theory Key Ideas • What patterns of heredity were explained by Mendel’s hypotheses? • What is the law of segregation? • How does genotype relate to phenotype? • What is the law of independent assortment?

2. Explaining Mendel’s Results • Mendel hypotheses are collectively called the Mendelian _________ of ________ • explains _____ patterns of ______. In these patterns, two of several _______ of a gene combine and result in one of several possible ________. • __________ traits result from different ________ of genes. _______ version of a _________ is called an ________.

3. Explaining Mendel’s Results • Each ________can ____to a _______ trait. • _____ can come ____ either ________ because each ________ of _______ is _____________ when _________ form during __________. • ______ one of the _____ is _______ on to _________.

4. Alleles

5. Explaining Mendel’s Results • An ________ that is fully ____________ whenever it is ______ is called __________. • An ______ that is not ________ when a ________ allele is ______ is called ______. • A _______ allele is ________ only when there is ____ dominant allele ____________. • __________ may also be called _________ or ____________.

6. Random Segregation of Alleles • _______ pairs ____ _______ during _____ • ______ decides which _____ from each parent will be ______ on. • the law of ________ holds that when an organism ________ gametes, _____ pair of _______ is ________ and each ______ has an _____ chance of _________ either one of the _________. • http://images2.clinicaltools.com/images/gene/ad_diagram_large.jpg

7. Mendel’s Findings in Modern Terms • ________represent the function of alleles. • ________ allele is shown as a _______ letter. • Polydactyly is dominant • D represents the presence of the dominant allele • _____ allele is shown as a ________ letter • Normal number of fingers & toes is recessive • d represents the recessive allele • Offspring _______ show a _____ for ____ allele that they _________. Instead, __________ of alleles determine traits. (ex. Dd, dd or DD) • Dd or DD • dd

8. Mendel’s Findings in Modern Terms • The set of _______ ___________ of alleles that an ______ has for a character is called the ___________. • The __________ trait that _________ from the genotype’s set of alleles is called the __________. • Thus, ________ determines ____________.

9. Mendel’s Findings in Modern Terms • If an individual has two ________ alleles of a ______ gene, the individual is _______ for the related character. (ex. dd or DD) • If an individual has two ________ alleles of a ______gene, the individual is _________ for the related character. (ex. Dd)

10. Mendel’s Second Experiments • A ______-cross involves two ________, such as seed color and seed shape. • Mendel used dihybrid crosses in his second experiments and found that the _______ of one _________ did ____ affect the _________ of another character. • In modern terms, the law of _________ ________holds that during _______ formation, the _______ of each gene segregate ____________.

11. Dihybrid Crosses

12. Mendel’s Second Experiments • Genes are said to be _____ when they are_____ together on ____________. • Scientists now know that many genes are ______ to each other as parts of chromosomes. • ______that are _________ close together on the same chromosome will ____ separate __________. • The only genes that follow Mendel’s law of independent assortment are those that are far apart.

13. Summary • Mendelian theory explains simple patterns of inheritance. In these patterns, two of several versions of a gene combine and result in one of several possible traits. • In modern terms, the law of segregation holds that when an organism produces gametes, each pair of alleles is separated and each gamete has an equal chance of receiving either one of the alleles. • Genotype determines phenotype. • In modern terms, the law of independent assortment holds that during gamete formation, the alleles of each gene segregate independently.